Safety valve

Abstract

A safety valve comprises a pressure receiving hole ( 20 ), an actuation chamber ( 21 ), a discharging hole ( 22 ) and an alloy accommodating chamber ( 25 ). An alloy ( 27 ) of a low-temperature melting point is accommodated within the alloy accommodating chamber ( 25 ). A sealing plate ( 33 ) seals the pressure receiving hole ( 20 ). This sealing plate ( 33 ) has a portion, which faces the pressure receiving hole ( 20 ), provided with a breakable sealing portion ( 35 ) that breaks up with a predetermined pressure. An actuator ( 28 ) is arranged within the actuation chamber ( 21 ). The actuator ( 28 ) has one end formed with a first back-up portion ( 30 ) which supports the breakable sealing portion ( 35 ) and has the other end formed with a second back-up portion ( 31 ) which is supported by the alloy ( 27 ).

1. A safety valve comprising a pressure receiving hole ( 20 ), an actuation chamber ( 21 ), a discharging hole ( 22 ) and an alloy accommodating chamber ( 25 ), a sealing member ( 34 ) sealing the pressure receiving hole ( 20 ) so as to be able to cancel the sealing, the sealing member ( 34 ) being supported by an alloy ( 27 ) of a low-temperature melting point accommodated within the alloy accommodating chamber ( 25 ),
 the sealing member ( 34 ) being composed of a sealing plate ( 33 ), this sealing plate ( 33 ) having at least a portion, which faces the pressure receiving hole ( 20 ), provided with a breakable sealing portion ( 35 ) that breaks up with a predetermined pressure, 
 an actuator ( 28 ) being arranged in the actuation chamber ( 21 ), the actuator ( 28 ) having one end formed with a first back-up portion ( 30 ) which supports the breakable sealing portion ( 35 ) and having the other end formed with a second back-up portion ( 31 ) which is supported by the alloy ( 27 ) of the low-temperature melting point. 
 
   
   
     2. The safety valve as set forth in  claim 1 , wherein the second back-up portion ( 31 ) has a surface supported by the alloy ( 27 ), which is formed larger in area than the breakable sealing portion ( 35 ) opposed to the pressure receiving hole ( 20 ). 
   
   
     3. The safety valve as set forth in  claim 1 , wherein the sealing plate ( 33 ) has a peripheral edge portion at which a gasket ( 32 ) is airtightly arranged. 
   
   
     4. The safety valve as set forth in  claim 1 , wherein the sealing plate ( 33 ) has a side opposite to the actuation chamber ( 21 ), which side is communicated with an interior space ( 6 ) of a gas cylinder ( 2 ) and the breakable portion ( 35 ) is adapted to break up with a gas pressure lower than a pressure normally used within this gas cylinder ( 2 ). 
   
   
     5. The safety valve as set forth in  claim 1 , wherein the first back-up portion ( 30 ) is inserted into the pressure receiving hole ( 20 ) positioned downstream of the breakable portion ( 35 ) and has a periphery to which an annular second sealing member ( 37 ) able to airtightly slide on an inner surface of the pressure receiving hole ( 20 ) is attached.